An Indian court has rejected a government attempt to reduce charges against a former Union Carbide official arising from one of the world's worst industrial disasters.

Thousands of people were killed in the central Indian city of Bhopal in December 1984 when gas leaked from a chemical factory belonging to Union Carbide. BBC News Online looks back at how the catastrophe unfolded.

It began without warning in the dead of the night, while the poor residents of Bhopal's slums slept.

A dense cloud of lethal gas escaped from the pesticide plant on the outskirts of the city and, like a phantom, rolled into the ramshackle homes of the nearby shanty town.

Then, picked by brisk winds blowing across India's central plains, it moved onwards into Bhopal, a city of 90,000 people.

We could barely see the road through the fog, and sirens were blaring. We didn't know which way to run

Ahmed Khan, resident

Nearly 3,000 people died in the first few days and tens of thousands suffered terrible side-effects. It was one of the world's worst industrial accidents.

Many - particularly children and the elderly - died in their beds as the gas seeped into their homes.

It took an average of three minutes for the victims to die.

The plant's alarm system - which could have given some last-minute warning - failed to go off for a number of hours.

When the siren did eventually sound, many did not realise it meant they had to run for their lives.

They hid from the foul-smelling fumes in their shacks. Their bodies were later discovered when police broke down the doors that were locked on the inside.

Hospitals swamped

Others, including women clasping babies, fled only to collapse in the street. Many were later found, huddled, sick and dying in city's doorways.

Many people were treated for respiratory problems

"We were choking and our eyes were burning," resident Ahmed Khan, was quoted as saying at the time. "We could barely see the road through the fog, and sirens were blaring. We didn't know which way to run."

Chaos reigned. "Everybody was very confused. Mothers didn't know their children had died, children didn't know their mothers had died and men didn't know their whole families had died," a local police officer said.

"Anyone who was left alive ran away blindly."

The city's two hospitals were swamped. For days after, people lay on the floors coughing and vomiting.

Doctors struggle

Some were temporarily blind, others complained of dizziness, all had problems breathing.

Estimates say that some 50,000 people were treated in the first few days.

At first, medical experts were in the dark. They had had little experience of MIC and were unsure of the long-term damage to people.

Some were forced to refer to the history books to explain the horrifying effects of the chemicals and how survivors could be treated.

It emerged that some of the victims would have suffered the same agonising deaths as soldiers in World War I when chemical weapons were first used.

The chemicals that formed the lethal cloud were, experts discovered, direct descendants of the gases that caused massive casualties on the battlefields.

There were immediate reports of acute eye and breathing problems, and kidney and liver failure. Many pregnant women had to be given abortions.

For days afterwards, funeral pyres cast a glow over the city and the stench of death mingled with the smoke of the cremations. Mass burials were also conducted.

Herds of oxen lay dead and the bodies of goats littered the roadsides where they used to roam.

Leaves on the trees were yellow and shrivelled - crops in the fields were scorched and covered with a fine white film.

The atmosphere in Bhopal was declared free of the gas after eight hours.

But the physical and psychological ramifications of that short space of time on 3 December 1984 will continue for a long time to come.